by TFH Magazine on January 29, 2010 at 9:09 am

By Ted Judy

Here’s a horror story that happened in my fish room that I hope nobody has to experience, although I know that the cause of disaster is the norm for most people rather than the exception. I went shopping for breeder tetras or barbs at one of the stores I buy a lot of fish from and found some great looking tiger barbs Puntius tetrazona, lemon tetras Hyphessobrycon pulchripinnis, and head-and-tail light tetras Hemigrammus ocellifer. The fish looked to be in excellent health and were all large enough to try to spawn almost immediately. When I got them home I discovered that I did not have anywhere to quarantine them until I was ready to spawn them, so I took a gamble and put the tiger barbs in a community aquarium with some larger rainbowfish and the tetras in a different community tank with several other tetra species. I made a poor choice…

Within a week all of the rainbow fish in the tank with the tiger barbs and about half of the fish in the tank with the new tetras started dying. They were attacked by a very rapid infection (probably protozoan parasites, bacteria, or a combination of the two) that caused the fish to start gasping at the surface, develop a nasty mucous all over their body, and pass away within 24 hours of showing signs of the infection. The really weird part was that most of the new fish did not get sick (only one lemon tetra and one head-and-tail light tetra died). The losses included an entire colony of adult emperor tetras Nematobrycon palmeri I had for three generations, six of eight adult Melanotaenia sp. ‘Moorhead River’ rainbows and all of my Glossolepis pseudoincisus, the Tami river rainbow, that were almost large enough to spawn. No other tank in the room was affected. Whatever wiped out my fish came in on those new acquisitions.

This Pelvicachromis taeniatus was shipped to the author with both protozoan and bacterial infections. Since the fish was mailed, an assessment of its health prior to purchasing did not happen.

I am totally at fault for the loss of those fish. I know better than to not quarantine what I bring into the fishroom, especially fish that are purchased from an aquarium store. This is not a knock on stores. There is not much a store can do to prevent diseases from coming into their tanks. To properly quarantine all of their new stock a store would need half as much tank space in the back room as they have in the front. Plus the store would need the financial security to expend thousands of dollars on fish and hold onto them for two or more weeks before starting to see a return on that investment. I have only seen a couple stores set up that way, and both were the retail front of a larger wholesale operation. And even then the wholesale part of the businesses did not sit on fish for two weeks to see if they were clean of infectious diseases.

These Mikrogeophagus ramirezi looked great in the store, but they were all infected with gill flukes and started dying two days after being purchased.

Most pet stores will mark a tank ‘do not sell’ when they see signs of sick fish, but in the case of my scenario the fish looked great and did not get sick from whatever they passed on to the other fish in the tank. There was no way to predict that is going to happen, and the only way to possibly prevent it would have been to quarantine the new fish properly.

This Pelvicachromis taeniatus was wild caught and came in with black blotches all over it. This was diagnosed as skin flukes and was easily cured in quarantine.

Quarantining fish is not as simple as just tossing them into a tank and waiting. The aquarium needs to have a mature biological filter and be free from diseases to begin with. Putting a dozen or more fish into a tank that has not been cycled does not have an upside. You are either going to be doing a lot of needless water changes to prevent an ammonia spike, or you will neglect that chore and end up with dead fish.

There are a couple ways to maintain the biological filter in a quarantine tank between fish purchases. The easiest way is to keep fish in the tank. A few zebra danios will do the trick.

You can also maintain the filter with a fishless-cycling system. This process involves adding ammonia and nitrite to the tank to feed the bacteria, and frequent testing for the nitrogen compounds to make sure that cycling is taking place. It takes more time, attention and chemicals to go the fishless route. I make do with danios.

The third option is to just keep buying lots of fish and rotating them through the quarantine tank. That is the unintended system that I use. I usually get out to the stores to buy new fish once a month, so the day before I go I evacuate the quarantine tanks (assuming the fish are healthy), do a thorough cleaning and set the tank up for new fish.

The quarantine process I use has two phases. Phase one is to get rid of all protozoan parasites. These little unicellular horrors are hard to diagnose until they are so numerous they are hard to kill. A bad protozoan infection leads to secondary bacterial infections that are even harder to cure. Ich and velvet are the two protozoan parasites most of us are aware of, but there are actually many species that we should be worried about. The morning of the day I plan to get new fish I add to the quarantine tank a full dose of medication designed to kill protozoans (I use a product with metronidazole in it), 1 teaspoon of aquarium salt per 10 gallons (most of these parasites prefer soft water) and crank up the temperature to 78° to 80°F. The heat will speed up the life cycle of the parasites, which is important because the medications will not always work on all the life stages. The medications need to be in the tank through the protist’s full life cycle to be 100% effective.

After the fish are in the tank I will do a 20% water change every other day and add just enough medication and salt to maintain the proper concentration of each in the tank. This first phase of the quarantine lasts for 10 days. Phase two starts with a lowering of the temperature to 73° to 75°F. I continue doing a 20% water change every other day, but now I do not redose the medications. If the fish are a hard water species (such as Lake Malawi and Lake Tanganyika fish) I will continue to add salts, but my tap water is only moderately hard. Phase two lasts for another 10 days, and at the end the fish (assuming they are not showing signs of poor health) are ready to go into tanks with other fish. If at any time during the process I see signs of disease I will try to diagnose the problem and treat accordingly. Once the problem is cured the quarantine starts again at phase two.

A quarantine tank is a simple set up.

The best case scenario is that there is nothing wrong with the fish. Careful observation of the fish in the store before purchasing will prevent most problems. I will not buy fish from a tank that has another noticeably ill fish in the same tank. If there are a lot of tanks in the store that seem to have problems I will pass on buying fish at all that day. Passing up the opportunity to buy something really rare or cool is something I have had to do many times.

The most important aquariums in my fish room are the quarantine tanks. They prevent something from coming in a wiping out what has grown to be a large and valuable (biologically and monetarily) collection of fish. I have discovered that some species, especially egg scatterers, condition very well while they are in quarantine. I have spawned pairs straight from the quarantine tank, and after they produce eggs it is back into the quarantine tank that they go. If they happen to end up with some infection I need to get rid of, the small spawning tanks are very easy to disinfect.

Quarantine is as important to the hobbyist with one tank as it is to a breeder with a fishroom. There is nothing more discouraging than adding a new fish directly to a well-established community and wiping it out. I have done it more times than I like to remember. I have a 10-gallon tank with a heater, glass top and air-driven sponge filter is all you need for quarantine. Even a 10 inch fish can live in a tank that small for the time needed to make sure it is healthy. If you are not using quarantine, you should be. The alternative is a gamble that you really do not want to lose… I know.